Interstate Aircraft and Engineering Corporation entered the aircraft manufacturing field in 1940 with the S-1A Cadet, a tandem seat monoplane. The prototype delivered to the U.S. Army Air Forces (AAF) was designated XO-63 and has the distinction of being the last airplane to use the “O” designation. When the United States entered World War II, the AAF contracted with Interstate for 250 of the S-1B1 variant and designated them L-6. Another eight aircraft were built with the designation L-8 for the Bolivian Air Force.

While the S-1B1 was faster, stronger, and could be operated in a more rugged environment than the comparable Piper L-4, the Interstate L-6 Cadet cost almost three times as much. The aircraft had significant overheating problems that were only partially solved. It had the dubious distinction that fewer L-6 aircraft and variants (a total of 259) were built than any other AAF liaison aircraft. The L-6 and L-8 were used for transport, liaison exercise, and flight training primarily in the United States. Interstate was based in El Segundo, California.


Wingspan: 35 ft 6 in
Length: 23 ft 5 in
Height: 7 ft 3 in
Empty weight: 1,103 lb
Max. takeoff weight: 1,650 lb
Wing area:
Armament: None
Engine: Continental A65-8 or Franklin 4ACG-199-H3
Crew: Two (pilot and passenger)
Cost: $6,000


Max. speed: 114 mph / 99 kt
Cruise speed: 105 mph / 91 kt
Rate of climb:
Range: 540 miles
Service ceiling: 16,500 ft
Wing loading: 7.45 lb/sf

The Interstate S-1A at Cannon Field makes a Fall foray.
L-6 Interstate S-1A operating out of Cannon Field.
L-6 Interstate S-1A at Cannon Field, May 1982.

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If you prefer to give by mail, send your check payable to: Alamo Liaison Squadron, 2352 S. Loop 1604 W., San Antonio, Texas 78264. Please write “Donation” in the memo line.